1. Technical Field
The present invention relates to a transconductance adjustment circuit, a circuit device, and an electronic apparatus.
2. Related Art
With the spread of portable wireless apparatuses in recent years, a wireless circuit device has been demanded that is smaller in size and low in power consumption. For example, the wireless circuit device has been realized on one chip, by using a complex band pass filter (a complex BPF) circuit configured from an operational transconductance amplifier (OTA) and a capacitor, as a filter circuit.
However, because a characteristic variation in a transconductance and a passive element due to variations in the IC manufacturing process and variations in power source voltage, temperature, and the like cannot be avoided, there is a problem in that a variation in a characteristic of a filter occurs and as a result, operation of the wireless apparatus is unstable.
With regard to this problem, techniques for compensating for the variations in the characteristic of the filter by adjusting the transconductance of OTA are disclosed in U.S. Pat. No. 7,319,731, JP-A-8-204504, and JP-A-2003-142987. However, the techniques are problematic in that the degree to which a phase error of the complex BPF circuit is detected is insufficient and it is difficult to compensate for the variation in the characteristic of the filter with high precision.